Fix nav to match new TOH titles

[jbogarthyde]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• angular.io application / infrastructure changes
• Other... Please describe:

What is the current behavior?

Previous TOH PR changed page titles, but missed TOC (left-nav) titles
https://angular.io/tutorial/toh-pt3
https://angular.io/tutorial/toh-pt4

Issue Number: N/A

What is the new behavior?

TOC titles match, slight update of titles

Does this PR introduce a breaking change?

• Yes
• No

[mary-poppins]

You can preview 9e00729 at https://pr35126-9e00729.ngbuilds.io/.

[mary-poppins]

You can preview 80457f6 at https://pr35126-80457f6.ngbuilds.io/.

[mary-poppins]

You can preview 38bf4fc at https://pr35126-38bf4fc.ngbuilds.io/.

[IgorMinar]

lgtm, thanks!

[mary-poppins]

You can preview d3312c0 at https://pr35126-d3312c0.ngbuilds.io/.

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